A German newspaper publisher says it has filed an appeal to Turkey's highest court against the incarceration for the past five months of a German-Turkish reporter.

Deniz Yucel, who works for the daily Die Welt, was arrested Feb. 14 in Istanbul. Turkish authorities accuse him of disseminating terrorist propaganda and inciting hatred, as well as espionage and ties to the outlawed Kurdistan Workers' Party, or PKK - allegations Yucel denies. He hasn't been formally charged.

Die Welt's publisher, WeltN24 GmbH, said it filed a complaint Tuesday to the Constitutional Court in Ankara against Yucel's continued imprisonment and violation of its press freedom in the case.

WeltN24 director Stephanie Caspar said Wednesday the company "will exhaust all legal means available to us to defend the freedom to report of our correspondent and the publisher."

Also Wednesday, Germany's foreign ministry said it has summoned the Turkish ambassador to demand the immediate release of an arrested human rights consultant.

Human rights consultant and trainer Peter Steudtner was arrested Monday and is being held in pre-trial detention on suspicion of aiding a terror group. Chancellor Angela Merkel has called the detention unjustified.

Ministry spokesman Martin Schaefer said that Foreign Minister Sigmar Gabriel was breaking off his vacation to discuss relations with Turkey.

Turkey has launched a wide-ranging crackdown on journalists, human rights campaigners, and people it says are suspected of supporting an attempted coup last year. .

Summoning a country's ambassador is a sign of sharp displeasure in diplomatic practice.